Owing to their excellent magnetic properties, Nd—Fe—B permanent magnets have been used in an increasingly wide range of applications. Recently, also in the field of rotating machines such as motors and power generators, permanent magnet rotating machines using Nd—Fe—B permanent magnets have been developed to follow the trend toward miniaturization, weight reduction, performance improvement, and energy saving of devices.
A permanent magnet in a rotating machine is under such an environment that the permanent magnet is extremely likely to be demagnetized because of exposure to high temperature due to heat generated by windings and an iron core and also because of a demagnetizing field generated by the windings. For this reason, there is a demand for a Nd—Fe—B sintered magnet which has a coercivity at or above a certain level, and an as-high-as-possible remanence. Here, the coercivity is an indicator of heat resistance and demagnetization resistance, while the remanence is an indicator of the magnitude of a magnetic force. An alloying process by grain boundary diffusion is known as a method for manufacturing an R—Fe—B sintered magnet having a high coercivity wherein R represents at least one element selected from rare earth elements inclusive of Y and Sc (Patent Document 1). In addition, by using the alloying process by grain boundary diffusion, a permanent magnet rotating machine has been proposed which comprises an R—Fe—B sintered magnet being free from the reduction in remanence and having a high coercivity especially at an end portion of the permanent magnet (Patent Document 2). Patent Document 3 proposes an arrangement of permanent magnets in which the space inside an axial gap-type permanent magnet rotating machine can be used at a high efficiency.